1. Technical Field
The present invention relates generally to devices for controlling the load imposed by a windshield wiper to the windshield of an automotive vehicle, and more specifically to a mechanism for adjusting such load responsive to reciprocal rotative movement of the windshield wiper driving shaft.
2. Description of the Prior Art
The problems and technical considerations considered in the setting of the forced to be imposed by the wiper arm and a windshield wiper mechanism of an automobile to urge the wiper against the windshield are well appreciated in the prior art. On the one hand, sufficient loading of the wiper is needed to overcome the lifting of the wipers from the windshield surface at high vehicle speeds, while on the other hand providing sufficient load to overcome the tendency of blades to lift the high speed may result in sticking and shattering of the blades under load speed operation where the lift is not present to counterbalance the loading force imposed at assembly.
A variety of approaches have been used in the automotive industry to effect loading of the wiper arm and hence the wiper blade in the direction of the windshield. One of the most common schemes involves the use of an extension spring grounded at one end on the wiper arm and at the other end on wiper structure through which the wiper arm is rotated. To make the force of this spring adjustable in response to the diverse loading requirements referred to above, the industry has made a number of attempts at devising suitable mechanisms exemplary of such attempts as that shown in U.S. Pat. No. 4,698,872 to Watanabe. Such devices have been found to be unsuitably heavy and expensive to manufacture, and the Watanabe device in particular requires subjected evaluation of the load by the operator of the vehicle and actuation of the switch mechanism to effect change in load.